Thanks Jaro, I have added your citation in the manual including a text reference: http://trac.osgeo.org/grass/changeset/45620
(while I was at it, I have also turned the table into a real HTML table). best Markus On Thu, Mar 10, 2011 at 1:54 PM, Jaro Hofierka <[email protected]> wrote: > Hi Markus, > > The r.sun model is described in this paper: > > Šúri, M., Hofierka, J. (2004): A New GIS-based Solar Radiation Model and Its > Application to Photovoltaic Assessments. Transactions in GIS 8, pp. 175-190. > ... > > The coefficients coefbh, coefdh are defined in the section 3.2 Computing > radiation under overcast conditions - eqs. (41), (42). > These are beam and diffuse components of the clear sky index. > That means the r.sun module can compute a clear-sky radiation right away, > however if you want a real-sky radiation (with the effects of cloudiness) > then you need some kind of coefficient saying how much the clear-sky > radiation is attenuated by the cloudiness. > Therefore you have to use raster maps with spatial distribution of these > coefficients separatelly for beam and diffuse radiation. > > I hope this helps. > > Best wishes, > > Jaro > > > Markus Neteler wrote: >> >> Hi Jaro, >> >> on the GRASS list the email below appeared which I cannot really >> answer. Do you have any hints for us? If ok, I would relay your answer >> to the list then. >> >>> From the manual: >> >> coefbh=string >> Name of real-sky beam radiation coefficient input raster map [-] >> coefdh=string >> Name of real-sky diffuse radiation coefficient input raster map [-] >> >> "Besides clear-sky radiations, the user can compute a real-sky radiation >> (beam, diffuse) using coefbh and coefdh input raster maps defining the >> fraction of the respective clear-sky radiations reduced by atmospheric >> factors (e.g. cloudiness). The value is between 0-1. Usually these >> coefficients can be obtained from a long-terms meteorological >> measurements." >> >> Thanks >> Markus >> >> On Sat, Mar 5, 2011 at 1:30 AM, TimNorwey<[email protected]> wrote: >>> >>> Hy >>> >>> I´m using GRASS GIS for the first time and I´m going to use the r.sun >>> model >>> for a project. >>> >>> When I was reading the explanation of the model, some questions appeared. >>> One is left. >>> I don´t understand the input parameter/raster coefbh/coefdh. >>> >>> Both of them can be values between 0-1 and they are described by >>> atmospheric >>> factors such as cloudiness. This is what is written in the explanation. >>> But >>> how do I determine coefbh/coefdh? What other factors are influencing >>> them? >>> How are the parameters combined, so that a value between 0-1 is given? Is >>> it >>> possible to determine them in a not too complicated way? >>> >>> I already read one post on coefbh/coefdh. Unfortunately, I didn´t >>> understand >>> it. >>> >>> I´m looking forward to get some answers. >>> >>> Thanks >>> >>> -- >>> View this message in context: >>> http://osgeo-org.1803224.n2.nabble.com/r-sun-ambiguities-about-coefbh-coefdh-tp6090593p6090593.html >>> Sent from the Grass - Users mailing list archive at Nabble.com. >>> _______________________________________________ >>> grass-user mailing list >>> [email protected] >>> http://lists.osgeo.org/mailman/listinfo/grass-user >>> >> > _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
